Previously, such devices have relied for their operation upon the movement of a pool of mercury to open or close the contacts of the switch. Numerous arrangements of such switches have been devised. However, all tilt switches and shock sensors which employ a mercury contact are disadvantageous because mercury is an extremely toxic material. Therefore, it is necessary for people manufacturing tilt switches and shock sensors to take precautions against poisoning by inhalation of mercury vapors, ingestion of mercury or touching of mercury. Additionally, the casings of tilt mercury switches and shock sensors must be strongly made and well sealed so that there is no danger of mercury escaping when the switch or sensor is damaged.
A further disadvantage of mercury tilt switches and shock sensors is that the mercury is difficult to dispose of safely when the switches and sensors are scrapped.